Extensive microneedle research has been conducted to enhance the efficiency of transdermal drug delivery. It has been expected and shown through experiments in vivo that microneedles can increase the skin permeability to deliver drugs by physically penetrating stratum corneum on epidermis without pain and scar. Microneedles have been fabricated using various kinds of materials, including ceramics, metals, and polymers. For example, a combination of surface and bulk-micromachining techniques was used to fabricate micro-hypodermic needles from a silicon wafer. The manufacturing cost may be, however, too high for low-cost applications such as daily multiple usages for patients. In this work, the designs of a microneedle and a runner system suitable for the successful fabrication using micro injection molding have been proposed. The mass-production of microneedles can be accomplished using micro injection molding.